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THERMAL ANNEAL EFFECTS ON CARBON-HYDROGEN LVMs IN AlGaN M. O. Manasreh*, and B.D. Weaver** * Department of Electrical and Computer Engineering, University of New Mexico, Albuquerque, New Mexico 87131 ** Naval Research Lab, 4555 Overlook Ave, SW, Washington, DC 20375 ABSTRACT Thermal annealing effects on carbon-hydrogen (C-H) complexes defects in AlGaN grown on sapphire by metalorganic chemical vapor deposition (MOCVD) technique have been investigated using Fourier transform infrared spectroscopy (FTIR). The CH complexes in AlGaN, formed either during growth or by proton irradiation, exhibit five local vibrational modes (LVMs) due to the symmetric and asymmetric vibrational stretching modes of C-H in CHn (n=1-3) defect complexes. It was found that the annealing temperature (Ta) of 500oC is sufficient enough to dissociate most of the C-H complexes in AlGaN samples. A turning point annealing temperature is found around 300oC for un-irradiated Mg-doped sample, below which the total integrated area of the C-H LVMs continued to increase with increasing annealing temperature and reach the maximum value around 300oC. At Ta > 300oC, the total integrated area of the C-H LVMs starts to decrease and the C-H complexes seem to be completely depleted at Ta > 600oC. The depleted C-H LVMs were observed to partially recover after thermal annealing at Ta > 500oC and waiting for aging periods of several days. This recovery behavior is explained in terms of the hydrogen being remained inside the crystal after the dissociation of C-H complexes, subsequent diffusion and recombining again with carbon atom to reform C-H complexes. INTRODUCTION Optoelectronic devices based on III-nitrides and their ternary alloys have a broad range of application due to their wide direct band-gaps covering the spectral range from visible to ultraviolet. GaN has unique applications in blue, green and ultraviolet-blue light-emitting diodes, detectors and laser diodes [1-4]. III-nitride material system also shows tremendous potential in the field of high-temperature and high-power electronics because of their superior materials parameters [5]. Omnipresent impurities such as carbon, hydrogen and oxygen play detrimental and beneficial roles in fabrication processes. For example, hydrogen can passivate the acceptor Mg [6-8] in GaN. Hydrogen can be easily incorporated into III-nitride during or after the growth of the materials [8]. Ion irradiation represents a very attractive tool for several technological steps, such as electrical and optical selective-area doping, dry etching and electrical isolation, in III-nitride based devices’ fabrication. Compare to the understanding of ion beam process in mature semiconductors (i.e. Si and GaAs), the understanding of the complex ion beam process in III-nitrides is still at its infancy. Therefore, understanding of thermal annealing behavior of complexes defects will help the understanding of dopant incorporation and application of ion implantation. In this paper, we report on some results of thermal annealing behavior of C-